Civil Aviation

The Ju 86 could fly higher than 39,000 ft

The Junkers Ju 86 served dual roles as both a twin-engine medium bomber and a civilian airliner, officially entering operational service in 1936. Originating in Germany during the early 1930s, and by 1938, around 470 units of the aircraft had been manufactured.

The bomber variants of the Ju 86, which included the A/D/E/G/K models, featured a four-person crew comprising a pilot, navigator, radio operator/bombardier, and gunner. The Ju 86P could fly higher than 39,000 ft (12,000m) where it was felt to be safe from enemy fighters.

The British Westland Welkin and Soviet Yakovlev Yak-9PD were developed specifically to counter this threat.

Its defensive armaments were limited to three 7.92mm MG15 machine guns, positioned at the nose, dorsal, and a retractable ventral spot, the latter of which, when deployed, likely impacted the aircraft’s aerodynamic performance.

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The most extensively produced versions were the D and K models, with the K designated as the export variant and the G model distinguished by its rounded glass nose.

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The aircraft was equipped to carry a relatively modest bomb load of 1,000kg (2,200 lb), stored vertically in the central bomb bay.

Development and Design

Developed by the German aeronautics company Junkers, renowned for its pioneering all-metal aircraft constructions, the Ju 86 was envisioned to fulfill dual roles seamlessly, serving both the civil aviation sector and the military front, a reflection of the growing militarization in Europe alongside the need for commercial air transport expansion.

A Ju 86 P high-altitude reconnaissance plane, equipped with Jumo 207 turbocharged diesel engines.
A Ju 86P high-altitude reconnaissance plane, equipped with Jumo 207 turbocharged diesel engines.

The design of the Ju 86 was a harmonious blend of functionality and innovation, aimed at maximizing efficiency and performance. Its most distinctive feature was its twin-engine configuration, which was a strategic choice to ensure reliability and power.

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The engines chosen were the Junkers Jumo 205 diesel engines, known for their fuel efficiency—a crucial factor for both extended commercial flights and long-range military missions. These engines represented a significant step forward in aviation technology, offering enhanced performance while maintaining economical fuel consumption.

The aircraft’s structure was a marvel of engineering, utilizing Junkers’ pioneering techniques in all-metal aircraft construction. The monoplane design featured a low-wing configuration, which was instrumental in providing stability and lift, crucial for the varied roles the aircraft was designed to fulfill.

Reducing Drag

The incorporation of retractable landing gear was a forward-thinking design choice, reducing drag and thus improving the overall aerodynamics and performance of the aircraft.

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This feature underscored the Ju 86’s modernity at a time when aviation design was rapidly evolving. Junkers’ hallmark duralumin corrugated skin was a key aspect of the Ju 86’s design, lending the aircraft structural strength without a significant weight penalty.

Formation of German Luftwaffe Junkers Ju 86 A or D bombers in 1937 (Source: Flightglobal, November 11, 1937, p. 466).
Formation of German Luftwaffe Junkers Ju 86 A or D bombers in 1937

This design choice was not merely functional but also emblematic of Junkers’ commitment to durability and reliability, ensuring that the aircraft could withstand the rigors of both civilian and military use.

The versatility of the Ju 86 was further exemplified in its adaptability to various configurations, catering to different needs and missions.

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The bomber variant was equipped with bomb bays and defensive armaments, transforming the aircraft into a tool of military strategy, while the airliner version was designed with passenger comfort in mind, featuring a cabin that could accommodate passengers and cargo, illustrating the aircraft’s dual-use potential.

Civilian Use

Upon its introduction to the civilian market, the Ju 86 was envisioned as a modern, efficient airliner capable of meeting the growing demands for air travel, which was becoming increasingly popular and commercially important during the 1930s.

The civilian variant, known as the Ju 86Z, was designed to offer reliability, comfort, and efficiency, traits that were essential for attracting airlines and passengers in an era where competition among aircraft manufacturers was intense.

Lufthansa Ju 52 and Ju 86 airliners during the late 1930s.
Crazy to think that not many survive. Lufthansa Ju 52 and Ju 86 airliners during the late 1930s.

The airliner version of the Ju 86 was adapted to prioritize passenger comfort and operational efficiency. It featured a spacious cabin, capable of accommodating up to ten passengers, providing them with a level of comfort that was competitive with other airliners of the time.

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The aircraft’s design focused on creating a smooth flying experience, with the all-metal, low-wing monoplane structure offering stability and quietness, which were key selling points for airlines and travelers alike.

Despite its innovative design and capabilities, the Ju 86 faced challenges in the commercial aviation market. It was operated by several airlines, including prestigious names like Lufthansa, Swissair, and South African Airways, signifying its acceptance in international routes and its potential as a competitive airliner.

Intense Competition

These airlines utilized the Ju 86 on various routes, exploiting its range and payload capacity to serve their expanding networks.

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However, the aircraft’s commercial success was somewhat limited by the rapid advancements in aviation technology and the intense competition from other aircraft manufacturers, who were also vying for dominance in the lucrative civil aviation market.

The Ju 86 had to compete with more advanced designs that were beginning to emerge, offering greater speed, capacity, and luxury, which gradually overshadowed the Ju 86’s early achievements.

Ju 86 G - observe the radial engines and the curved, glass-encased nose.
Ju 86G – observe the radial engines and the curved, glass-encased nose.

Furthermore, the dual-use design of the Ju 86, while innovative, meant that it was a compromise between the differing requirements of a civilian airliner and a military bomber.

This compromise, although showcasing Junkers’ engineering prowess, may have limited the aircraft’s appeal in a market that was increasingly looking for specialized designs tailored to the specific needs of commercial aviation.

Military Adaptation

The Junkers Ju 86’s transition into military service exemplifies the period’s drive to adapt civilian aviation technology for military purposes, it was the quickest and cheapest route.

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This adaptation was part of a significant shift as nations sought to modernize their military capabilities in response to the evolving geopolitical landscape and the lessons learned from World War I.

As tensions in Europe escalated in the 1930s, there was a clear impetus for countries to bolster their air forces, leading to the militarization of existing aircraft designs.

The aircraft featured advanced technological aspects for its time, including variable-pitch propellers, retractable landing gear, and a fully glazed and streamlined nose on later models.

The Ju 86, initially conceived as a commercial airliner, was reconfigured to serve as a medium bomber, capitalizing on its robust design, reliable performance, and the strategic advantage provided by its twin-engine configuration.

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This military variant was designed to fulfill a range of roles, including bombing, reconnaissance, and transport, demonstrating the adaptability of the original airframe to various military requirements.

The bomber version of the Ju 86 was equipped with bomb bays capable of carrying a significant payload, although relatively light compared to later bomber designs.

Ju 86 and the Spanish Civil War

The defensive armament was minimal, typically comprising a few machine guns strategically placed to protect the aircraft from enemy fighters.

The Ju 86’s adaptation for military use also involved enhancements to its range and payload capacity, ensuring it could undertake extended missions crucial for strategic bombing campaigns.

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One of the notable early deployments of the Ju 86 in a military capacity was during the Spanish Civil War, where it served with the Condor Legion, a unit composed of military personnel from Nazi Germany who supported Franco’s Nationalists.

The Ju 86 saw combat action during the Spanish Civil War, providing the Luftwaffe and the Condor Legion with valuable operational experience.

This conflict served as a testing ground for the Ju 86 and other military technologies, providing valuable insights into the aircraft’s performance in combat conditions and its suitability for various operational roles.

Throughout World War II, the Ju 86 was utilized on various fronts, from the early campaigns in Poland and the Low Countries to the more extended operations in the Mediterranean and North Africa.

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Its roles diversified from strategic bombing to reconnaissance missions, where the aircraft’s range and capability to fly at high altitudes were particularly valued. However, as the war progressed, the limitations of the Ju 86 became increasingly apparent.

The advancement of anti-aircraft defenses and the introduction of faster, more agile enemy fighters rendered the Ju 86 vulnerable, leading to its gradual withdrawal from front-line service.

Ju 86 Goes Operational

As briefly touched on above, the Ju 86 bomber underwent field testing by the Condor Legion during the Spanish Civil War, where four Ju 86D-1 units were deployed to Spain in early February 1937.

The operational experience was short-lived, as one aircraft was downed by Republican fighters around late February to early March 1937. Following the loss, a replacement was dispatched from Germany.

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However, subsequent landing mishaps damaged two more, leading to the sale of the remaining aircraft to the Nationalist air force, where they served until the Civil War’s conclusion.

Production of the Ju 86 was relatively short-lived, with the last models being manufactured in the late 1930s as newer bomber designs took precedence.
Production of the Ju 86 was relatively short-lived, with the last models being manufactured in the late 1930s as newer bomber designs took precedence.

Comparative evaluations indicated the Ju 86 was generally less effective than the Heinkel He 111 tested concurrently. At the onset of World War II, a single group of Ju 86 bombers engaged in the 1939 Polish invasion but were quickly phased out. The diesel-engine variants were retired, and the radial-engine models were reassigned to bomber training schools.

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By late 1942, in a desperate bid to aid the besieged 6th Army at Stalingrad, available Ju 86s were mobilized from training schools, forming transport groups at Tatsinskaya Airfield.

The aircraft, ill-suited for such missions, endured significant losses before Soviet forces overran the airfield, ending their airlift involvement due to their insufficient range for alternative airfields.

Hungary also Utilized the Ju 86

In 1940, the Luftwaffe experimented with the Ju 86P prototype, featuring a longer wingspan and a pressurized cabin, enabling high-altitude flights believed to be beyond the reach of enemy fighters.

However, this variant faced new threats as the British Westland Welkin and Soviet Yakovlev Yak-9PD were designed specifically to counteract such high-flying adversaries.

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On the Allied front, 17 early-model Ju 86s, previously operated by South African Airways, were repurposed for military use at the war’s outbreak, initially for coastal patrols and later in the East African Campaign. These aircraft were gradually phased out as more advanced planes became available.

Junkers Ju-86 airliner
Cockpit of the Junkers Ju-86 airliner

Hungary also utilized the Ju 86, notably against Slovakian targets in the Slovak–Hungarian War of 1939 and later in the initial stages of Operation Barbarossa. The type was eventually retired from Hungarian frontline service in favor of the Caproni Ca.135.

The Luftwaffe, encouraged by the Ju 86P prototype’s performance, converted several older bombers into high-altitude Ju 86P-1 bombers and Ju 86P-2 reconnaissance planes.

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These aircraft operated successfully over various theaters, including Britain, the Soviet Union, and North Africa, until escalating losses and the development of enemy countermeasures led to their withdrawal from service in 1943.

The subsequent development of the Ju 86R, designed for even higher altitudes, did not proceed beyond the prototype stage, marking the end of the operational use of this aircraft series in active service.

The Ju 86’s varied use across multiple fronts and roles encapsulates its complex service history, reflecting the challenges and rapid technological advancements of aerial warfare during that era.

Powerplants of the Ju 86

The Ju 86 was notable for incorporating several innovative features. Its diesel engines, initially installed in some variants, were a novel choice, offering potential advantages in fuel efficiency and range. However, the diesel engines proved to be less reliable and were eventually replaced with more conventional petrol engines in later models.

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The aircraft initially featured 600 hp Jumo 205 diesel engines, marking it as the first German bomber to be powered by a diesel plant. These engines were favored for their high efficiency and greater fire safety.

Jumo 205 cutaway
The Junkers Jumo 205 aircraft engine was the most renowned in a series of diesel engines for aircraft produced by Junkers.

However, their substantial weight and, as combat tests in Spain later revealed, their insufficient power led to the replacement of the diesel engines with the more powerful 845-horsepower BMW 152 radial piston air-cooled engines, which were Pratt-Whitney Hornet engines produced under license in Germany.

In 1939, with the aim of maximizing the flight range for the newly developed Ju 86P reconnaissance variant, the aircraft reverted to diesel engines, this time utilizing an enhanced high-altitude Jumo 20 “A model delivering 680 hp.

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These engines allowed for a maximum flight altitude of 12,100 meters, and the aircraft could sustain flight for 2.5 hours at 10,000 meters, making it unreachable by the fighter aircraft of that era.

The engines were paired with three-bladed metal propellers of the Hamilton or Junkers type that allowed variable pitch adjustments mid-flight. NACA cowls, featuring adjustable air outlet slots, covered the engine installations, and the coolant radiators were positioned beneath the engines.

Jumo-205C diesel

While the Ju 86 saw some success in its export versions, its performance in the Luftwaffe was less favorable. German propaganda couldn’t overshadow the persistent issues with the Jumo-205C diesel engines, leading to low combat readiness for the Ju 86D models. Problems included piston seizures and exhaust pipe welding corrosion.

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The Ju 86-V9, a conversion of the Ju 86D-1 to incorporate the BMW-132F engine, underwent testing in spring 1937 and demonstrated improved reliability over its diesel predecessors. Consequently, Junkers was prompted to shift production to models powered by the BMW-132F engines.

The BMW 132 engine was extensively utilized in the transport sector, notably serving as the primary powerplant for the Junkers Ju 86. This role cemented the BMW 132 as one of the most crucial aircraft engines for civilian aircraft during the 1930s.

This led to the Ju 86E-1 variant, which started being delivered in late summer 1937, with the BMW-132F engine producing 810 hp at takeoff and maintaining 650 hp at 4500 meters.

This engine upgrade significantly boosted the aircraft’s reliability and increased its fuel capacity to 1500 liters, though the overall performance characteristics remained largely unchanged.The Ju.86E-1 was produced alongside various export models of the Ju-86K bomber, catering to Hungary, Sweden, Portugal, and Chile.

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A total of 30 Ju86E-1 aircraft were manufactured with BMW-132F engines, and a slightly larger number were equipped with BMW-132N engines, offering enhanced takeoff power. The subsequent variant, known as the Ju 86E-2, was also favored by Austria, illustrating the model’s broad, albeit specialized, application.

The aircraft also contributed to the development of high-altitude flight technology. The Ju 86P and Ju 86R variants, designed for high-altitude reconnaissance and bombing, respectively, included pressurized cabins—a relatively new feature at the time—and supercharged engines to enable operation at extreme altitudes.

Ju 86 G series

A notable limitation of the Ju.86 was the restricted visibility for pilots during takeoff, a problem that persisted until the aircraft’s tail lifted off the ground. To address this issue, designers repositioned the cockpit forward and introduced a fully glazed front section.

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An MG-15 machine gun was incorporated into the right front panel. These modifications were first implemented and tested on the Ju.86 E-1 model in early 1938, leading to the designation of the updated aircraft as Ju.86-V10.

Based on this prototype, the final 40 production units underwent modernization to include the new nose design and equipment for instrument flight conditions, aligning them with the Ju.86E-2 specifications.

Identified as the Ju.86G-1, this variant commenced rolling off the Dessau assembly lines in late spring to early summer of 1938, marking the end of the production line for this model. In total, 390 units were delivered, encompassing transport models and those assembled in Sweden, excluding those produced under license.

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By late autumn 1938, the Luftwaffe’s inventory of Ju.86s peaked. On September 19, 1938, Air Force records indicated that the bomber squadron consisted of 235 bombers of various models, 200 of which were deemed combat-ready.

Ju 86 Units Were Reassigned

This included 159 Ju 86A-D models, 43 Ju 86E, and 33 Ju 86G variants. Subsequently, the Ju 86 began to be phased out from front-line service, a process that hastened by early 1939. By the onset of hostilities in September, only one group, IV/KG.1, still operated these bombers, fielding 30 Ju 86G-1 units. These aircraft were soon retired following the campaign in Poland.

The diesel-powered variants were quickly phased out of service, with most VMW-132 engines being reassigned to bomber flight schools and other training units. By the end of 1942, Ju 86 aircraft were deployed to hastily formed transport groups K.Gr.z.b.V.21 and 22 to aid the Stalingrad encirclement.

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With 58 aircraft, they commenced operations but proved to be wholly unsuitable for the transport role. Both groups suffered the loss of 42 aircraft by the end of January, leading to their disbandment in March.

The 16 remaining Ju 86 units were reassigned to training units, although several were later used in anti-partisan operations in the Balkans during 1943-44.

Post-war, the Ju 86 faded into obscurity as newer, more advanced aircraft designs took precedence. Few examples of the aircraft survive today, with most having been scrapped or lost to combat during the war.

Fortunately, Sweden is a nation committed to the preservation of its aviation history, which encompasses maintaining a specimen of their Ju 86 aircraft.

This preservation effort is particularly significant given the rarity of the Junkers Ju 86 twin-engine bombers; the sole surviving and intact model, a Ju 86K-4 (Werk Nr. 0860412), is currently exhibited at the Swedish Air Force Museum (Flygvapenmuseum) located in Malmslätt, just outside Linköping.